The expansion of the third generation (3G) networks around the world and the increase in bandwidth for data transmission increased the offer of new services. The new data services and the Internet access using the mobile devices made 3G networks to be integrated with other networks for data communication.
Data and mobile networks are becoming seamless and the information traffic is increasing due to the broad, and increasing, bandwidth available. The air interface resources required for data traffic makes the energy consumption to increase, reducing the battery lifetime from the 3G mobile devices. The impact to exchange messages to allocate physical resources from mobile devices and the network in a third generation network is higher than in a second generation network due to the air interface channels characteristics and the protocol structures.
In fact, some of the most popular smartphone applications are also some of the greatest generators of signaling traffic. Social networking applications, in which friends are connected with each other for extended periods of time, inherently involve frequent back and forth messages or status updates. Instant messaging services, VOIP applications, and other popular services, are just some of the examples while if someone is “connected” it would not be uncommon for him to simultaneously leverage multiple social networking applications.
One of the concepts used for mobile devices is Always-On. This is used for mobile devices that need to be reached by other devices or service and it remains connected to the network with a valid network address. Applications like e-mails, which use e-mail push and VoIP, are examples of services which require the mobile device to be reached anytime by the access network.
Another important aspect to be considered is the radio resource allocation, which is dynamically performed according to the data traffic. The Radio Resource Control (RRC) has two states in 3G networks: Idle and Connected. When a device is connected to the network, it is generally consuming at least some network resources, while transitioning between the various RRC states can generate a little or a lot of signaling traffic. The RRC state has an impact on the battery life with some states requiring considerably more current consumption than other states.
The idle state is the mode in which the mobile device is basically dormant and not communicating with the network, although it does listen certain broadcast messages. In this state, the radio portion of the phone is not consuming any network resources and it consumes the least amount of power, or in the range of only 5 mA. The connected stated is divided into the following modes: Cell Dedicated Channel (Cell_DCH), Cell Forward Access Channel (Cell_FACH) and Cell Paging Channel (Cell_PCH). Said states indicate various levels of being connected to the network, even though the definition of being connected varies widely between the three states, as follows:                Cell_DCH is the state, in which a dedicated channel is allocated to the mobile device. It is used for data transmission when the data amount to be transferred is high. When a mobile phone is in this state, it is consuming the most network resources, while the drain on the battery is also at its highest level, about 200 mA or higher.        Cell_FACH is the common channel used when there is a low volume of data to be transmitted, or the data flow reaches a threshold set by the core network. The energy consumption of mobile devices in this case is about 100 mA.        Cell_PCH is an optional state, in which the phone can receive a network paging signal to check if there are packets to be transmitted through the downlink. The energy consumption in this state is about 1% or 2% of the Cell_DCH mode.        
Another aspect to be considered is the transition criteria. One state transition criteria is based on the Buffer Occupation (BO) level of the mobile device. The BO stores the data to be sent, and indicates the traffic flow of data packets. The measurement of the BO is sent from the mobile device to the network, that decides to change RRC state or not. If a reconfiguration is necessary, the message is sent from the network to the mobile device. This message contains the RRC State Indicator field, which is meant to inform which is the new state that the mobile device must switch to.
Another mechanism used to trigger state transition is the timeout due to inactivity periods of time. There are three inactivity timers that are used to determine when a handset or smartphone should move to a lower state following a specified period of time of inactivity.
FIG. 1 shows the characteristic curve for receiving a simple packet. T1 timer refers to the period of time of inactivity within the Cell_DCH state before the 3G device is sent to a lower state. T2 timer is associated with the Cell_FACH state and it is used in a similar manner for determining how long the 3G device should remain in the Cell_FACH state without any activity. Finally, T3 timer determines how long the handset should remain in Cell_PCH before returning to the idle state. The average current for each state is presented in FIG. 2.
Timeouts and resources consumption is another important aspect to be considered. It is simple to show that the bigger the T2 timer is, more energy is consumed by the mobile device. On the other hand, the shorter the timeout value is, more resources from the core network will be spent to perform new connections.
In real networks, the carriers setup the T2 timeout with very large values that can reach up to 30 or 50 seconds. With this strategy, the carrier keeps connection active to prevent reconnections if subsequent packets are received in a short interval (multiple signaling), and save resources from new connections
Considering such scenarios, it is possible to find trade-off values, in which the time-outs makes that no unnecessary energy is consumed from the mobile device and therefore no further resources of the network is compromised.
The U.S. Pat. No. 6,807,159 filed on Oct. 25, 2000 discloses a system, method, and computer program product for carrying out the method for managing power consumption in a master driven time division duplex wireless network comprising optimizing power consumption while maintaining quality of service requirements for end-to-end packet delay by adjusting the polling interval for each slave in low power mode based on the incoming traffic at the slave. According to said document, when no packet is being received, the system switches from active to stand-by mode. Also, prediction method for arrival of packets is used, as well as the device is maintained in stand-by mode when there is no traffic being received or sent. The main constrain imposed by the teachings of said document is that a fixed algorithm for traffic prediction is used, which represent a huge prior art drawback.
The U.S. Pat. No. 7,155,261 filed on May 1, 2003 describes a method of saving power in a mobile device during a cell updating procedure in a wireless communication system. The mobile device uses a first timer and a second timer to monitor its internal operations. If only one timer is running, a running timer is assigned to be the first timer. If both timers have no associated Radio Access Bearers (RABs), the first timer is started. Therefore, said document proposes a better check for timeouts, causing the device to leave the CELL_DCH state and going into the idle state, thereby saving power. Differently, the present invention relates to receiving data (IP packets), whereas said US document is linked to the process of selection/re-selection a cell. Also, the involved timeouts are different. The present invention employs T1, T2 and T3, which are used for disconnections of the RRC state machine at the network core side during the “change state” process, whereas according to said US document, T314 and T315 are also timers of RCCRRC state machine but the energy saving method of this document focus the “cell update” process. The present invention comprises a dynamic process for interrupting the timer and disconnect the device, whereas said US document checks the ideal conditions for initializing the timer during the selection/re-selection process.
According the embodiments of such document, an enhanced check of the timers is carried out, causing the device to leave the CELL_DCH state to the IDLE state, saving power. Said document deals with cell selection/reselection, whereas the present invention relates to data receiving (IP packets).
The US document US 20090285142 filed on Apr. 5, 2009 discloses a system and method for maximizing the standby time of mobile communication devices that have Wi-Fi or other high energy-consuming network interfaces, by predicting in real time actionable silent periods of time (ASPs) of the interface and shutting the interface down during these ASPs. Standby times are significantly increased, resulting in longer periods of time of operation before battery charging is required, while keeping minimal the probabilities of missing incoming data packets when the interface is turned off. The method of reducing energy consumption of a device that operates intermittently with extended periods of time of inactivity between intermittent operations, comprising the steps of: monitoring operation of said device to detect periods of time of inactivity; predicting the duration of a detected period of time of inactivity; and turning off power to said device for a period of time substantially corresponding to said predicted duration. According to the teachings of said document, prediction model is used for silence intervals. Also, there is no change in the protocols, but in the ON/OFF periods of time for transmission and reception. In addition, the energy consumption is controlled by the mobile device, with no interference of the network. Nonetheless, when using such teachings, packets may be lost. In addition, separate receivers are required, which may pose extra problems for implementation.